THE crackdown on Yemen's growing opposition movement is getting much nastier. On Friday snipers hidden on rooftops opened fire on the crowds gathered for prayers outside Sana'a University. At least 39 were killed and around 200 injured, according to doctors talking to the BBC. Scenes of chaos were reported at the makeshift hospital that the demonstrators have set up within their camp.

Fridays have seen the largest demonstrations in the Yemeni capital. Tens of thousands have gathered for prayers at the makeshift camp set up by anti-regime protesters at the gates of Sana'a University, in part to mourn those killed the week before. Today's dead brought the number killed throughout the protests to around 80.

Such violence can only mean that Yemen's embattled president, Ali Abdullah Saleh, is losing his already long-tenuous grip on power as more people throughout the country join the calls for his ouster. Shortly after the shooting, the gruff former soldier declared a state of emergency. America's President Barak Obama immediately condemned the violence and said that those responsible should be held accountable. Those are worrying words for Mr Saleh who relies heavily on American aid; he received $300m of it last year.

Since protests began in late January, Mr Saleh has tried to quell the dissent with concessions. He raised salaries and said he would step down when his term ends in September 2013. In recent weeks he has been trying to negotiate with the opposition, going so far as to offer a deal that would give more power to parliament and local authorities. After today's bloodshed it seems unlikely his opponents will be keen to negotiate any more.

"There is no longer any possibility of mutual understanding with this regime and he has no choice but to surrender authority to the people," Yassin Noman, the current president of Yemen's opposition, told Reuters.

The future looks bleak. If Mr Saleh is not prepared to step down now, there will be more violence. Opposition protesters, who have so far done little more than throw stones, may retaliate with more force if they find themselves repeatedly coming under fire. In one of the world’s most heavily armed countries, civil war is a real possibility.